The present invention relates generally to an annular seal assembly adapted to be coaxially positioned about a rotatable shaft and, in particular, to a seal assembly which includes a polytetrafluoroethylene (PTFE) sealing element and is designed for use ih a vehicle air conditioning compressor.
Rotary shaft seal assemblies which are utilized in vehicle air conditioning compressors are subject to a wide variety of operating conditions based upon the speed of the compressor shaft and the ambient air temperature. One of the most commonly used compressor shaft seals is a mechanical face type seal comprising a rotatable carbon sealing ring which is adapted to sealingly engage a polished surface of a stationary ceramic ring. The ceramic ring includes an outer periphery which is adapted to be secured to the main body of the compressor. The carbon sealing ring is adapted to rotate with the compressor shaft and is biased into sealing engagement with the ceramic ring. While such a seal assembly has proved to be relatively satisfactory, the assembly is relatively expensive to manufacture.
Annular seal assemblies which utilize a polytetrafluoroethylene (PTFE) seal element for sealingly engaging a rotatable shaft have been proposed. Examples of such PTFE seal assemblies can be found in U.S. Pat. Nos. 3,572,732 and 3,771,799. However, due to the environment in which they must operate, these types of annular PTFE seal assemblies have proved to be unsatisfactory when utilized as a shaft seal in a vehicle air conditioning compressor.